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Solar power: Morocco blazes ahead

Boris Sedacca reports on how Morocco is blazing ahead with concentrated solar power

In February 2016, Morocco launched Noor 1, the first phase of the largest concentrated solar power (CSP) plant in the world, which aims in time to produce enough energy for more than one million Moroccan households.

In November 2011, the World Bank approved US$297 million in loans to Morocco to help finance the Ouarzazate 500MW Concentrated Solar Power Plant Project. A US$200 million loan was provided by the International Bank for Reconstruction and Development, and another US$97 million loan came from the Clean Technology Fund (CTF), a US$5.6 billion funding window of the Climate Investment Funds (CIF).

Ultimately aiming to supply power to 1.1 million Moroccans by 2018, the Moroccan Solar Agency (MASEN) Ouarzazate solar complex is among the largest CSP plants in the world, as part of a plan to deploy 2,000MW of solar power generation capacity by 2020. Ouarzazate Phase 1 will generate the first 160MW. It is anticipated that the plant will reduce the country’s energy dependence by about 2.5 million tons of oil, while also lowering carbon emissions by 760,000 tons per year.

“CSP is the greatest energy technology you have probably never heard of,” says CIF Manager Mafalda Duarte. “The International Energy Agency estimates that up to 11% of the world’s electricity generation in 2050 could come from CSP.”

Exporting energy to Europe

“Once Noor I, Noor II and Noor III are up and running, the plant could eventually start exporting energy to the European market. It will increase Morocco’s energy independence, create 200 jobs during the power plant operation and 1,600 jobs during construction, and increase the installed capacity of solar power stations from 22MW in 2013 to 372MW in 2018.”

Global installed CSP-capacity has increased nearly tenfold since 2004 and grew at an average of 50% per year during the past five years according to REN21, the Renewable Energy Policy Network for the 21st Century. The total project cost of Noor I CSP is US$841 million.

A CSP technology developed by Desertec claims to create a new carbon-free network linking Europe, the Middle East and North Africa. The plan was backed mainly by German industrialists and it predicted production of 15% of Europe's power by 2050, but more on that later.

Morocco is a major partner in Desertec and as it has barely 1% of the electricity consumption of the EU, the idea is that it will produce more than enough energy for the entire country with a large energy surplus to transmit to Europe. More energy is said to fall on the world's deserts in six hours than the world consumes in a year.

The Sahara offers proximity to Europe, has virtually no population and more intense sunlight than Europe. CSP installations placed in the Sahara generate around 30% more power per area than in southern Spain, according to Morocco's renewable energy agency CDER.

Noor 1, 2 and 3

The share of renewable energy in total electricity generation is expected to increase from 4,345GWh (13%) in 2013 to a target of 5,501GWh (42%) by 2020. Energy dependency should be reduced through additional electricity production from the 160MW Noor 1 and the 350MW Noor 2 and 3 in 2018.

This has aroused considerable debate in the media about interconnectors to mainland Europe. There is already reported to be a mid-sized 700MW interconnector to Spain under the Straits of Gibraltar that mostly carries power the other way at present. Interconnectors balance peak loads and outages, while adding resilience.

High voltage direct current (HVDC) electric power transmission uses DC for the bulk transmission of electrical power over long distances in favour of the more common alternating current (AC) power transmission systems. HVDC losses are about 3% per 1000km, far more efficient than AC.

Some argue that transmission is not a problem, so long as the power generators are large enough to warrant it. China, for example, has already installed over a dozen HVDC cables longer than 1000km, several of which are over 2,000km. Shanghai for example draws 7GW from one hydro station over 2,000km away.

Meanwhile, the European Commission has contributed €5 million to the Mediterranean Solar Plan. The goal of this project is to promote the production and use of renewable energies. Mediterranean partner countries produce solar energy and transmit generated electricity to Europe.

Desertec deserters

Ouarzazate was originally the location chosen in 2011 by the Desertec consortium for a solar plant that would be part of a US€400billion project that would supply much of Europe with solar electricity through power lines under the Strait of Gibraltar. However, in late 2012 many of the investors, including Spain, Bosch and Siemens pulled out, and Morocco found alternative support from the Africa Development Bank.

The non-profit Desertec Foundation was founded in January 2009. In the autumn of 2009, a consortium of companies formed the Desertec Industrial Initiative (Dii), which included participants such as E.ON, Munich Re, Siemens and Deutsche Bank.

Despite Dii, Desertec is still going ahead with projects in Tunisia, Morocco and Algeria. The Desertec foundation is backing the Tunur project in Tunisia, a joint venture between Nur Energy, a British-based solar developer and a group of Maltese and Tunisian investors in the oil and gas sector.

Inside a CSP plant

CSP plants typically use 12m high parabolic mirrors that reflect sunlight onto pipework that contains a heat transfer fluid (HTF), typically thermal oil. This increases the temperature of the fluid to almost 400°C. The HTF is then used to heat steam in a standard turbine generator. The fluid is made up of a synthetic thermal oil solution that is pumped towards a heat tank containing molten salts that can store heat energy for three hours.

With vapour phase systems, heat is transferred at the saturation temperature of the vapour to provide uniform, precisely controlled temperature. In liquid phase systems, the temperature of the heating medium decreases as it gives off heat. Thus, the temperature of the medium at the inlet will be higher than its temperature at the outlet. This non-uniformity of temperature can be harmful to heat-sensitive products, even when it is reduced by increasing the circulation rate of the medium.

Noor 1 uses Dowtherm A HTF at a solar field inlet temperature of 293°C and outlet temperature of 393°C. The gross power block turbine capacity is 160MW (Net 143MW) from a steam rankine cycle output using wet cooling. Auxiliary fossil fuel backup is provided by a light fuel oil (LFO) boiler to keep the system warm. Two-tank indirect thermal storage provides capacity for up to three hours using molten salt.

Dowtherm A is a eutectic mixture of two very stable organic compounds, biphenyl (C12H10) and diphenyl oxide (C12H10O). These compounds have practically the same vapour pressures, so the mixture can be handled as if it were a single compound. Dowtherm A fluid may be used in systems employing either liquid phase or vapour phase heating. Its normal application range is 15-400°C, and its pressure range is from atmospheric to 10.6 bar.

Importance of analysis

Dr Chris Wright of thermal fluid supply and heat transfer expert, Global Heat Transfer, emphasises the importance of sampling and chemical analysis (SACA) of synthetic HTFs throughout their life cycle.

Wright explains: “SACA should be considered as an ongoing strategy to reduce unexpected operational downtime and spread the cost of maintenance as test results can be used to predict potential problems, to take corrective action as required and to maintain the condition of the HTF to extend the lifetime of CSP plant components.”

Older CSP plant can only generate electricity during the day when direct sunlight is available. More recently heat storage in the form of molten salts has been introduced to newer CSP plants to lengthen electricity generation times.

In Italy, Archimede is said to be the first CSP plant in the world to use molten salts to store heat and also as a HTF in parabolic collectors. The receivers developed by Archimede are designed to operate at up to 580° C with all types of heat transfer fluid used in current CSP power plants.

Molten salt, which is currently used as a heat storage medium, can be used as a working fluid without the 400ºC cap of regular oil, reaching temperatures up to 550ºC. A storage system heat exchanger can thus be eliminated, since the fluid circulating through the pipework to the storage system is the same.